Wire bonding structure and manufacturing method thereof

ABSTRACT

The present invention relates to a wire bonding structure, and more particularly to a manufacturing method for said wire bonding structure. The wire bonding structure comprises a die that connects with a lead via a bonding wire. At least one bond pad is positioned on an active surface of the die, and a gold bump is provided on the bond pad; furthermore, a ball bond can be positioned upon the gold bump. The bond pad and the gold bump can separate the ball bond and the die, which can avoid damaging the die during the bonding process.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation patent application of co-pendingapplication Ser. No. 12/358,604, filed on 23 Jan. 2009. The entiredisclosure of the prior application, Ser. No. 12/358,604, from which anoath or declaration is supplied, is considered a part of the disclosureof the accompanying Continuation application and is hereby incorporatedby reference.

This application claims priority of U. S. Provisional Application No.61/098,292 filed on 19 Sep. 2008 under 35 U.S.C. §119(e), the entirecontents of all of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a wire bonding structure, and moreparticularly to a manufacturing method for said wire bonding structure.

BACKGROUND

FIG. 1 is a diagrammatic illustration of a wire bonding structure inaccordance with a prior art. The typical wire bonding structure 10comprises a substrate 11 and a die 13. The die 13 comprises an activesurface 131 and a back surface 133, and is positioned on the top surfaceof the substrate 11. A bond pad 15 is positioned on the active surface131 of the die 13, and connected with a lead 19 by means of a ball bond171 and a bonding wire 173.

In the manufacturing process of wire bonding structure 10, the die 13can be positioned on the top surface of the substrate 11 by means of anadhesive layer 12. For example, the back surface 133 of the die 13 canconnect with the top surface of the substrate 11 via the adhesive layer12. Thereafter, a capillary 18 can be used to form the ball bond 171 onthe bond pad 15, and then form the bonding wire 173 to connect the ballbond 171 and the lead 19.

In general, the ball bond 171 and the bonding wire 173 are both made ofcopper, so that the cost of the manufacturing process of the bondingstructure 10 can be reduced. However, damage to the die 13 or the bondpad 15 may occur during the bonding process. For example, heat can begenerated when the ball bond 171 is formed on the bond pad 15, and inturn damage the die 13 and cause a reduction in the yield of the wirebonding structure 10.

SUMMARY OF THE INVENTION

It is the primary objective of the present invention to provide a wirebonding structure, wherein a bump is positioned between the bond pad andthe ball bond, and the ball bond shall not touch the bond pad or the dieto avoid damage to the die and/or the bond pad during the bondingprocess.

It is a secondary objective of the present invention to provide a wirebonding structure, wherein the bump is made of gold, and the hardness ofsaid gold is much lower than that of copper, tin, or aluminum, which canmaintain the structure and the functionality of the die during thebonding process.

It is another objective of the present invention to provide a wirebonding structure, wherein the bump is positioned between the bond padand the ball bond to increase the distance between the ball bond and thebond pad, which can improve the yield of the wire bonding structure.

It is another objective of the present invention to provide amanufacturing process for the wire bonding structure, wherein acapillary can be used to form the ball bond and the bonding wire, andthe efficiency of the bonding process can be improved.

It is another objective of the present invention to provide amanufacturing process for the wire bonding structure. A gold bump can beformed on the bond pad before bonding the ball bond and the bondingwire, which thus avoids the ball bond directly touching the bond pad.

In an aspect of the present invention, a wire bonding structure isprovided, comprising: a die comprising a first surface and a secondsurface; a bond pad positioned on said first surface of the die; a bumppositioned on the bond pad, wherein the bump comprises gold; a ball bondpositioned on the bump; and a bonding wire connecting the ball bond anda lead.

In an aspect of the present invention, a wire bonding structure isprovided, comprising: at least one first bond pad positioned on a firstdie; at least one second bond pad positioned on a second die; a firstbump positioned on the first bond pad; a second bump positioned on thesecond bond pad, wherein the first bump and the second bump bothcomprise gold; a ball bond positioned upon the first bump; and a bondingwire connecting the ball bond and the second bump.

In an aspect of the present invention, a manufacturing method of a wirebonding structure including a bond pad positioned on a die is provided,comprising the steps of: forming a bond pad on a die; forming a bump onthe bond pad, wherein the bump comprises gold; forming a ball bond onthe bump; and forming a bonding wire to connect the ball bond and alead.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagrammatic illustration of a wire bonding structure inaccordance with a prior art.

FIG. 2 is a diagrammatic illustration of a wire bonding structure inaccordance with an embodiment of the invention.

FIG. 3A to FIG. 3C are diagrammatic illustrations of the manufacturingprocess of a wire bonding structure in accordance with an embodiment ofthe invention.

FIG. 4 is a diagrammatic illustration of a wire bonding structure inaccordance with an embodiment of the invention.

FIG. 5 is a diagrammatic illustration of a wire bonding structure inaccordance with an embodiment of the invention.

FIG. 6 is a diagrammatic illustration of a wire bonding structure inaccordance with an embodiment of the invention.

FIG. 7A to FIG. 7D are diagrammatic illustrations of the manufacturingprocess of a wire bonding structure in accordance with an embodiment ofthe invention.

FIG. 8 is a diagrammatic illustration of a wire bonding structure inaccordance with an embodiment of the invention.

DETAILED DESCRIPTION

Referring to FIG. 2, there is shown a diagrammatic illustration of awire bonding structure in accordance with an embodiment of theinvention. The wire bonding structure 20 comprises a die 23 thatconnects with a first bond pad 29 via a bonding wire 273. Further, thedie 23 comprises a first surface 231 and a second surface 233, whereinthe first surface 231 can be an active surface and the second surface233 can be a back surface.

There is at least one bond pad 25 positioned on the first surface 231 ofthe die 23, and a bump 26 is positioned on the bond pad 25, wherein thebump 26 can be made of gold. A ball bond 271 can be positioned upon thebump 26, and connected with the first bond pad 29 by means of a bondingwire 273.

In one embodiment of the invention, the ball bond 271 and the bondingwire 273 can be made of copper, tin, or aluminum, and so on. Thehardness of gold is much lower than that of copper, tin, and aluminum,so by using gold damage to the bond pad 25 and/or die 23 can be avoidedduring the process of forming gold bump 26. Moreover, the ball bond 271is formed upon the bump 26 and does not touch the bond pad 25 and/or thedie 23, so that the structure and function of the die 23 and/or the bondpad 25 can be maintained after bonding the ball bond 271 and the bondingwire 273 on the bump 26,

Referring to FIG. 3A to FIG. 3C, there are shown diagrammaticillustrations of the manufacturing process of a wire bonding structurein accordance with an embodiment of the invention. There is a bond pad25 positioned on the first surface 231 of the die 23, and a bump 26 canbe formed on the bond pad 25 by ultrasonic vibration of metal diffusiontechnology. For example, a capillary 281 can be used to form the bump 26on the bond pad 25, wherein the bump 26 is made of gold, as shown inFIG. 3A. In addition, the bump 26 also can be formed on the bond pad 25by plating technology.

A capillary 283 can be used to form a ball bond 271 upon the bump 26, asshown in FIG. 3B. For example, a wire 27 is carried through thecapillary 283, and threaded through the capillary 283 for use in thebonding process. The end of the wire 27 protruding from the capillary283 is heated to a molten state by way of an electrical discharge or ahydrogen torch; the capillary 283 presses the molten wire 27 against thebump 26 to form the ball bond 271 upon the bump 26.

The capillary 283 can be used to form a bonding wire 273 to connect theball bond 271 and the lead 29, as shown in FIG. 3C. For example, afterforming the ball bond 271 on the bump 26, the capillary 283 can be movedfrom the bump 26 to the lead 29, and the wire 27 is pressed against thelead 29, thereby forming the bonding wire 273 between the bump 26 andthe lead 29. In addition, the wire 27 can be a copper wire, tin wire, oraluminum wire, and the ball bond 271 and the bonding wire 273 can bothbe made of copper, tin, or aluminum.

The die 23, the bond pad 25, and the lead 29, may be heated during thebonding process for the benefit of melting the wire 27. The capillary283 may include an ultrasonic vibration unit to form the ball bond 271and the bonding wire 273. Furthermore, a capillary with metal diffusiontechnology may be used to form the ball bond 271 and the bonding wire273.

The bump 26 is made of gold. As the hardness of gold is much lower thanthat of copper, tin, or aluminum, damage can be avoided to the dieand/or the bond pad 25 as the gold bump 26 is formed on the bond pad 25.Otherwise, the bump 26 formed on the bond pad 25 can act as a bufferstructure, so that the ball bond 271 cannot touch the bond pad 25 and/orthe die 23 directly during the bonding process, which can protect thedie 23 and/or the bond pad 25 from damage resulting from hightemperatures.

In one embodiment of the invention, the die 23 can be positioned on thetop surface of a substrate 21. For example, the second surface 233 ofthe die 23 can connect with the top surface of the substrate 21 via anadhesive layer 22, and the lead 29 may be positioned on the same ordifferent substrate 21. In addition, the substrate 21 can also be aleadframe, and the die 23 and/or the lead 29 can be positioned on theleadframe.

Referring to FIG. 4, there is shown a diagrammatic illustration of awire bonding structure in accordance with an embodiment of theinvention. The wire bonding structure 200 comprises a die 23 and asubstrate 21, and the die 23 may connect with the substrate 21 via anadhesive layer 22. Further, the die 23 comprises a first surface 231 anda second surface 233, wherein the first surface 231 can be an activesurface and the second surface 233 can be a back surface.

There are a lead 29 and a bond pad 25 positioned on the substrate 21 andthe first surface 231 of the die 23 respectively. A bump 26 that is madeof gold can be positioned on the bond pad 25. Furthermore, a ball bond271 can be positioned upon the bump 26, and connected with the lead 29by means of a bonding wire 273.

Referring to FIG. 5, there is shown a diagrammatic illustration of awire bonding structure in accordance with an embodiment of theinvention. The wire bonding structure 30 comprises a first die 331 and asecond die 333 that connect to each other. There is at least one firstbond pad 351 positioned on the first die 331, and at least one secondbond pad 353 positioned on the second die 333.

A first bump 361 and a second bump 363 are positioned on the first bondpad 351 and the second bond pad 353 respectively; the first bump 361 andthe second bump 363 are both made of gold. A bump 365 is positioned uponthe second bump 363, and a ball bond 371 is positioned upon the firstbump 361, and the ball bond 371 connects with the bump 365 by means of abonding wire 373. The ball bond 371 and the bump 365 are both made ofcopper, tin, or aluminum.

In another embodiment of the invention, there is no bump 365 positionedupon the second bump 363, and the ball bond 371 can connect with thesecond bump 363 by means of a bonding wire 373 directly, as shown inFIG. 6.

Referring to FIG. 7A to FIG. 7D, there are shown diagrammaticillustrations of the manufacturing process of a wire bonding structurein accordance with an embodiment of the invention. The first bond pad351 and the second bond pad 353 can be positioned on the first die 331and the second die 333 respectively. Thereafter, a capillary 381 can beused to form the first bump 361 on the first bond pad 351, and form thesecond bump 363 on the second bond pad 353, wherein the first bump 361and the second bump 363 are both made of gold, as shown in FIG. 7A.

After forming the first bump 361 and the second bump 363, a capillary383 can be used to form a bump 365 upon the second bump 363, as shown inFIG. 7B. Furthermore, the capillary 383 also can be used to form theball bond 371 upon the first bump 361, wherein the bump 365 and the ballbond 371 both can be made of copper, tin, or aluminum, as shown in FIG.7C.

After bonding the ball bond 371 on the first bump 361, the capillary 383can be moved from the first bump 361 to the bump 365. The wire 37carried in the capillary 383 can be pressed against the bump 365,thereby forming the bonding wire 373 between the first die 331 and thesecond die 333, as shown in FIG. 7D. In addition, the wire 37 can be acopper wire, tin wire, or aluminum wire, so that the ball bond 371, thebonding wire 373, and/or the bump 365 can be made of copper, tin, oraluminum.

Referring to FIG. 8, there is shown a diagrammatic illustration of awire bonding structure in accordance with an embodiment of theinvention. The wire bonding structure 40 comprises a die 43 thatconnects with a lead 49, wherein the die 43 can be positioned on asubstrate 411 and the lead 49 can be positioned on a leadframe 413. Thedie 43 comprises a first surface 431 and a second surface 433; the firstsurface 431 can be an active surface and the second surface 433 can be aback surface.

There is at least one bond pad 45 positioned on the first surface 431 ofthe die 43, and a bump 46 positioned on the bond pad 45, wherein thebump 46 can be made of gold. A ball bond 471 can be positioned upon thebump 46, and connected with the lead 49 by means of a bonding wire 473.

The present invention is not limited to the above-described embodiments.Various alternatives, modifications, and equivalents may be used.Therefore, the above embodiments should not be taken as limiting thescope of the invention, which is defined by the appending claims.

1. A wire bonding structure, comprising: a die comprising a firstsurface and a second surface; a bond pad positioned on said firstsurface of said die; a bump positioned on said bond pad, wherein saidbump comprises gold; a ball bond positioned upon said bump; and abonding wire connecting with said ball bond and a lead.
 2. The wirebonding structure of claim 1, comprising a substrate positioned undersaid second surface of said die.
 3. The wire bonding structure of claim1, wherein the material of said ball bond and said bonding wire is thesame.
 4. The wire bonding structure of claim 3, wherein the material ofsaid ball bond and said bonding wire is copper, tin, or aluminum.
 5. Thewire bonding structure of claim 1, wherein a capillary is used to formsaid ball bond and said bonding wire.
 6. The wire bonding structure ofclaim 1, wherein said first surface of said die is an active surface. 7.A manufacturing method of a wire bonding structure including a bond padpositioned on a die, comprising the steps of: forming a bump on saidbond pad, wherein said bump comprises gold; forming a ball bond on saidbump; and forming a bonding wire to connect said ball bond and a lead.8. The manufacturing method of claim 7, comprising the step of: using acapillary to form said ball bond and said bonding wire.
 9. Themanufacturing method of claim 7, wherein said ball bond and said bondingwire comprise copper, tin or aluminum.
 10. The manufacturing method ofclaim 7, wherein said bump is formed by plating technology.
 11. Themanufacturing method of claim 7, wherein said bump is formed by acapillary with metal diffusion technology.
 12. A wire bonding structure,comprising: a substrate; a lead positioned on said substrate; a diepositioned on said substrate, wherein said die comprises a first surfaceand a second surface; a bond pad positioned on said first surface ofsaid die; a bump positioned on said bond pad, wherein said bumpcomprises gold; a ball bond positioned upon said bump; and a bondingwire electrically connecting with said lead and said ball bond.
 13. Thewire bonding structure of claim 12, comprising an adhesive layerpositioned between said substrate and said die.